Thiocyanate

Abstract: A method is described for the rapid isolation and purification of bacterial genomic DNA. A total of 215 bacterial strains representing species of Campylobacter, Corynebacterium, Escherichia, Legionella, Neisseria, Staphylococcus and Streptococcus, were lysed with guanidium thiocyanate. DNA was prepared using just three other reagents and one high-speed centrifugation step. The method, which was applicable to both Gram-positive and Gram-negative bacteria, eliminated endogenous nuclease activity and avoided the need for phenol, RNase and protease treatments. The DNA was of high purity, high molecular mass and double-stranded.

Abstract: We have previously shown [Goto, Y., Calciano, L. J., & Fink, A. L. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 573-577] that beta-lactamase, cytochrome c, and apomyoglobin are maximally unfolded at pH 2 under conditions of low ionic strength, but a further decrease in pH, by increasing the concentration of HCl, refolds the proteins to the A state with properties similar to those of a molten globule state. To understand the mechanism of acid-induced refolding of protein structure, we studied the effects of various strong acids and their neutral salts on the acid-unfolded states of ferricytochrome c and apomyoglobin. The conformational transition of cytochrome c was monitored at 20 degrees C by using changes in the far-UV CD and in the Soret absorption at 394 nm, and that of apomyoglobin was monitored by changes in the far-UV CD. Various strong acids (i.e., sulfuric acid, perchloric acid, nitric acid, trichloroacetic acid, and trifluoroacetic acid) refolded the acid-unfolded cytochrome c and apomyoglobin to the A states as was the case with HCl. For both proteins neutral salts of these acids caused similar conformational transitions, confirming that the anions are responsible for bringing about the transition. The order of effectiveness of anions was shown to be ferricyanide greater than ferrocyanide greater than sulfate greater than thiocyanate greater than perchlorate greater than iodide greater than nitrate greater than trifluoroacetate greater than bromide greater than chloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: We demonstrate postsynthetic modification of CsPbBr3 nanocrystals by a thiocyanate salt treatment. This treatment improves the quantum yield of both freshly synthesized (PLQY ≈ 90%) and aged nanocrystals (PLQY ≈ 70%) to within measurement error (2–3%) of unity, while simultaneously maintaining the shape, size, and colloidal stability. Additionally, the luminescence decay kinetics transform from multiexponential decays typical of nanocrystalline semiconductors with a distribution of trap sites, to a monoexponential decay, typical of single energy level emitters. Thiocyanate only needs to access a limited number of CsPbBr3 nanocrystal surface sites, likely representing under-coordinated lead atoms on the surface, in order to have this effect.

Abstract: The thiocyanate dosimeter (10–2 mol dm–3 SCN– in O2-saturated water) has been standardised against the super-Fricke dosimeter (10–2 mol dm–3 FeII in O2-saturated 0.4 mol dm–3 H2SO4) using the hexacyanoferrate(II) dosimeter [5 × 10–3 mol dm–3 Fe(CN)64– in O2-saturated water] as a secondary standard. On the basis that G(FeIII)= 1.67 × 10–6 mol J–1 and IµFeIII= 220.4 m2 mol–1 at 304 nm and 25 °C in the super-Fricke dosimeter, we obtain GIµ[Fe(CN)63–]=(3.47 ± 0.06)× 10–5 m2 J–1 at 420 nm and GIµ(SCN)2˙–=(2.59 ± 0.05)× 10–4 m2 J–1 at 475 nm. These values remain unchanged when the solutions are saturated with air instead of O2 and are doubled in N2O-saturated solution.